Sound radiator



` Sept. l, 1931. R. v. L. HARTLEY 1,821,54'?

SOUND RADIATOR Filed March 3l, 1925 1 15 that of the driving means,

*i 20 sound radiator of Patented Sept. 1, 1931 UNITED STATES PATENT OFFICE RALPH V. L. HARTLEY, F SOUTH ORANGE, NEW JERSEY, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION 0F NEW YORK SOUND RADIATOR This invention relates to a sound radiator designed to act directly on the air and impart vibrations to the air from a relatively large surface.-

An object of this invention is to provide a vibratile member so shaped as to make vibration equally possible for all frequencies throughout the important frequency range in speech and music.

A further object is to providea vibrating system which offers to the air a low mechanical impedance comparable with that of the air and to the mechanical driving member a higher impedance comparable with thereby obtaining a system which faithfully imparts a large portion of the vibratory energy to the air.

In general, this invention comprises a light weight material in the form of a plane surface, or its structural equivalent, having one edge driven 'perpendicular to itself and a non-parallel opposite edge attached to a fixed support.

.25 The vibrating surface and the driving system are designed to make vibration substantially equally possible for all frequencies throughout the sound range and thus obtain uniform response and uniform imi 30 pedance.

A specific application of this invention, y more fully hereinafter described, comprises its application to a loud speaking receiver in the form of a plane surface or its struc- 'j35 tural equivalent having a trapezoidal or similar shaped sound radiator in which one non-parallel edge is attached to a torsional driving member so that torsional motion of this driving member imparts vibrational f motion perpendicular to the surface of the 45 lar to itself by having a transverse motion instead of a torsional motion. The motor element should preferably be attached to the torsional drive at the high frequency end, that is, the end where the sound radia- V 50 tor is narrowest.

Referring to the drawings, Fig. 1 is a general assembly side View of the sound radiator with supporting means and motor element. Fig. 2 is an end view looking towards the sound radiator' and showing the motor element. Fig. 3 is a side view of a plane sheet sound radiator of somewhat diiferent shape from that shown in Fig. 1. Fig. 4 is an end view of the plane sound radiator showing the attachment of he fixed and the4 vibra ile edges. Fig. 5 is a side view of a hollow stifened sound radiator. Fig. 6 is an end View of Fig. 5. Fig. 7 is a side view of a hollow stiffened sound radiator having its edges shaped similar to Fig. 3. Fig. 8 is an end View of Fig. 7.

In Fig. 1, the base plate and main supports for the mechanism are shown at 10, 11, 12 and 13. 14 is the sound radiator made of light weight material and is attached to the vibrating member 15 at one edge by means of the clamp 16 and at its oppositeedge to the non-parallel rigid support 18 by means of the clamp 17. The vibrating member 15 is supported at each end by means of knife edges or other suitable antifriction bearings 19 and 20. The fixed support 18 for the sound radiator is capable of being adjusted to permit the sound radiator 14 being placed under a greater or lesser tension. This adjustment is made and fixed by bolts 21, 22 and 23, which permit the sound radiator to be placed under tension, and to evenly take up the tension particularly when the adjustment is made by the screw 21 only. Screws 22 and 28 permit locking the member 18 in the position it takes when adjustment is first made by screw 21, and also permits placing a greater tension on one end of the sound radiator 24 is the motor element, consisting of any suitable driving means, such as shown in Egerton Patent No. 1,365,898 dated January 18,1921, suitably supported and connected to the sound radiator. The connection is such that vibration of the armature of the motor produces a torsional vibrational movement of the shaft or rod 15 which is attached to the driven than on the other.

edge of the sound radiator 14 in such a inanner that torsional vibration 15 imparts a vibrational motion to 14 perpendicular to its surface.

Fig. 2 is an end view of the motor element 24 and shows a means consisting of meinn bers :26, 27528 and 29 for connecting-the motor element to the driving member 15 so that vibration of the armature is ini:

parted- 4to 4the sound vradiator through torvsional vibra-tion of the driving member-115.

tire length of the diaphragm or4 it may'be. :made to increaseat a greateror lesser' rate Fig. 3 shows a side view of a modified shape of the sound radiator 30 in which the change in distance from the driven edge to the fixed edge as one'end is approached 'does not change .ing proportion-to .thefdistance along. thefradiator, as inthe case of a trapezoidalshaped sound .radiator shown vin Fig 1. Curving the edge of the sound .radiator `opposite the driven edge` permits distrib.

Iuting .the frequency absorptionI for. different frequencies along the diaphragm. 1n accordance with .anyy desired plan,y that is, the .oiniension ofthe diaphragm normal to the driven=edge may be made to increase unifornily with frequency .throughout the enthan uniformly.

vkFig. 4 is an end view of a flat sound radiatory showing:particularly the clamps 16 and 17 attached to its vibratile and fixed edges, respectively.

- supporting the sound radiator in any of its the exception bythe nieansfprovided for this purpose.

. half the wave length for the low frequency.

7 are of such design that porting and may or may not be pla-ced under. astatic stress bythe supporting members -15` The sound radiators shown in Figs. 5.and

and 18.

` The sound radiator may-be made prefer ably of parchment papei7 a good grade of drawing paper, blotting paper, fabric vniaterial'7 or other light weight material, such as aluminum.

The width of the sound radiator at the narrow end` should beapproxiinately onehalf the wave length for the high frequency and at the wider `end approximately ione- For the higherfrequencies the .narrower portionV of the sound radiator at the left This or similar methods of they are self-supwill absorb and radiate to the air most of the vib 'ational energy while for somewhat lower frequencies the vibrations will spread over the sound radiator towards the wider edge at the right and an area dependent on the frequency will be set into resonant vibration. The .relatively high mechanical inipedaiice due to this motion will be effectively in series with that of the remainder of the-rod, and so a'largeshare'voftlieenergy will-go-intothe sound radiator. For the lower frequencies the-sound radiator iin- -pendance will be low and the energy will be transmitted along the rod to a point where Iowing to theincreased width of the sound radiator, resonance is possible at that frequency. The energy will then pass over into the sound lradiator and be radiated to the air. The lower frequency limit of such a system would be determined 4by its size. As the velocity: of sound in the driving Vmember 15 may be made much greater :than that ofthe sound radiator made of such material as paper, the distribution of the various components along this structure would not introduce any appreciable distortion dueto the lower frequencies being retarded.

It will be obvious that the' driving inember 15 can be given translatory movement instead of rotary movement to drive the `sound radiator ifl desired. It will further be obvious'tliat the .motor elements may be placed at both ends of the driving ineiiiber 15 when thisniay be found desirable.

. It will be apparent tothose skilled. in vthe art .that various other modifications -of .the inventionniay be made andthat Vthe invention is not therefore limited to the specific structures that have beenillustrated but' its scope is defined in theappended claims.

' `Vhat is clainiedis:

. 1.* A large direct-acting sound radiator of light weightumaterial, means for tensioning said radiator, and means for drivingsaid sound radiator at substantially every point along an edge thereof.

.2. A large vdirect-acting sound radiator of `light weight material .having the .greater portion of one edgenttachedto a fixedsupt port vand the greater portion yof the opposite edge attached to a vibratile support.

' 3. A large direct-actiiig soundradiator of light weight materiali having. a. lvibratile edge, and .means for driving` the vibratile.

.edgefat substantiallyial-l points simultaneously .in adirectioii perpendicular tothe surface of the' sound. radiator.

.4. .Av largel direct-acting sound radiator consistingof a vibratile member havingone edge attached at substantially all points-to a fixed` support -and an f opposite 'non-parallel edge attached at substantially all 'points'` vto a vibratile'support.

5. A large direct-acting :soundifradiator consisting of a vibratile member of light weight material having a vibratile edge and a non-parallel opposite fixed edge, and means for varying the tension in the vibratile member.

6. A large direct-acting sound radiator, means for imparting vibrational forces simultaneously to all points along an edge of said radiator, and means for varying the static tension in said sound radiator.

7. A large direct-acting sound radiator consisting of a sound radiating member having a straight vibratile edge, and rotary means for driving the vibratile edge at substantially all points in a direction perpendicular to the surface of the sound radiator.

8. A direct-acting sound radiator consisting of two sheets of thin material, means for securing said sheets along one edge and means for imparting vibrations to another edge, said sheets being fastened together at their driven edge and at their fixed edge, and a sepa-rating member for holding said sheets apart along a line between said edges.

9. A large direct-acting sound radiator, means for tensioning said radiator and means for clamping two opposite edges of said sound radiator, one of said clamping means being fixed and the other' of said clamping means being vibratile to vibrate the said sound radiator in accordance with sound waves, each of said clamping means extending the full length of the edges clamped thereby.

10. In combination, a driving member, a large direct-acting sound radiator consisting of a vibratile member having two of its opposite edges non-parallel, one of said edges being attached to a fixed support, and a vibratile support connected in operative relation with said driving member and attached to another edge of said sound radiator.

11. In combination, a driving member, a large direct-acting sound radiator consisting of two sheets of thin material, means for securing said sheets along one edge, means for imparting vibrations to another edge, said sheets being fastened together at their driven edge and at their fixed edge, and a separating member for holding said sheets apart along a line between said edges, the driven edge of said sound radiator being connected in operative relation with said driving member.

12. A large direct-acting sound radiator comprising a vibratile member having one edge attached to a driving member and the opposite edge attached to a fixed support, the distance between the fixed support and the driving member increasing progressive- 1y along the length of said sound radiator.

13. A direct-acting sound radiator of light weight material comprising a vibratile memloer of variable width, the distance between the fixed edge and the driven edge being a non-linear function of the distance from either end of the sound radiator.

14. An acoustic device comprising a large direct acting sound reproducing means and an actuating device therefor including a rotary means, both of said means being joined throughout the greater portion of their lengths.

15. An acoustic device comprising a large direct acting diaphragm and actuating means therefor including a long rotary element driving said diaphragm at substantially every pointalong a straight line between two edges of said diaphragm.

16, An acoustic device comprising a large direct acting diaphragm and actuating means therefor including a long rotary element -driving said diaphragm along a straight line extending the greater part of the distance between two edges of said diaphragm.

17. An acoustic device comprising a large direct acting diaphragm and actuating means therefor including a rotary member substantially the length of one dimension of said diaphragm and connected thereto at every point along one element between two opposite edges of said diaphragm.

18. An acoustic device comprising a large direct acting diaphragm and actuating means therefor including a rotary member approximately the length of one dimension of the diaphragm and means connecting all points along a longitudinal element of said member to said diaphragm and between two opposite edges of said diaphragm.

19. An acoustic device comprising a tensioned sound radiator, a member rigidly secured to said radiator across one dimension thereof, and means for imparting vibrational forces simultaneously to all portions of said member.

20. A loud speaking diaphragm consisting of a plane sheet of metal having a density substantially that of aluminum supported at two opposite ends only and held under tension along its vibratory surface.

21. A loud speaking diaphragm consisting of a plane sheet of metal having a specific gravity greater than 2.7 and less than 3 supported at two opposite ends only and held under tension along its vibratory surface.

22. A direct acting diaphragm of loud speaking area comprising a quadrilateral plane sheet of thin flexible material held permanently in a stretched condition along its vibratory surface.

23. A direct acting diaphragm of loud speaking area comprising a quadrilateral plane sheet of thin flexible metal supported at two opposite ends only and held permanently stretched along its vibratory surface.

24, An acoustic diaphragm of loud speaking.a1ea having alengthequal vtoatv least i twice its 1 Width. and means for tensioning said diaphragm? in1tlie .direction of `one. di-

. nnensony only.

y v 25. AnVac-oustio':diaphragmofloudspeakw'ngfuarea 'comprising a:qnadrilaterall sheet of' metal: Ahaving a specific gravity greater ,than- 2.7 andg-less than Batensionediin'the ,cli-

rection of it length only, the length of said 1 wsheet being not-lessl'than twice its. Width.

In Witness whereof; IY hereunto subscribe my na1nevthisi27th :day of. March,` AMD.

VviRALPHf V. L. HARTLEY. 

